This is Dudley Observatory’s Skywatch Line for Friday, July 15, through Sunday, July 17, written by Sam Salem.
The Sun rises at 5:31am on Friday and sets at 8:32pm. The 82% illuminated Waxing Gibbous Moon sets at 2:13am on Friday; 2:52am on Saturday; 3:35am on Sunday; and 4:25am on Monday morning. The Full Moon occurs on Tuesday.
On Friday evening, the Moon appears 3 degrees above Saturn. The 1st-magnitude star Antares in Scorpius lies 10 degrees below the Moon. The Moon, Saturn, and Antares line up vertically in the south at dusk. Mars is positioned to the trio’s right. Saturn is the farthest planet you can easily see with your unaided eye. Right now, it’s about 9.3 Astronomical Units from Earth (9.3 times the Earth-Sun distance). Saturn is the second-largest planet after Jupiter. Its diameter is about 9.5 times bigger than the diameter of the Earth. Like Jupiter, Saturn is a gas giant world, composed of mainly hydrogen and helium.
A few minutes after sunset on Saturday, look for Venus just above the west-northwest horizon with fainter Mercury just 0.5 degrees (almost the diameter of the full Moon) above it. Venus is currently magnitude –3.9, and Mercury is –1.0, so you may be able to detect Venus with unaided eye once you locate them in binoculars. Mars and Saturn will line up with the Waxing Gibbous Moon this evening.
The best time to look for Uranus this weekend is shortly before twilight begins around 4am. Uranus then lies 40 degrees high in the northeast among the background stars of Pisces the Fish. A telescope reveals Uranus’ blue-green disk.
Draco is one of the characters JK Rowling named after a celestial object in her Harry Potter series. Draco, the Dragon, is among the earliest constellations to have been defined. Draco is a circumpolar constellation that is out all night long every night of the year. However, the summer months are the best times to see Draco up in the sky when the Dragon’s flashing eyes look down upon you. Draco lies between the Big and Little Dippers with its tail found between the bowl of the Big Dipper and the star Polaris. Draw an imaginary line between Altair and Vega, of the Summer Triangle, to find the Dragon’s eyes glaring at you. These two “eye” stars are Rastaban and Eltanin. These star names mean, “Snake Head” and “Dragon” in Arabic.
This weekend marks the birthdates of three pioneer astronomers. Jocelyn Bell Burnell, born in July 15, 1943, is a British astronomer who discovered the first four pulsars, at the age of 24, when she noticed an unusual rapid series of stellar radio pulse signal repeating every 1.337 sec. Giuseppe Piazzi, Born in July 16 Jul 1746, Italian astronomer who discovered the first asteroid, Ceres. Recent spectral observation by NASA’s Dawn spacecraft revealed that the Ceres’ mysterious bright spot is made of salt. Monsignor Georges Lemaître, born in July 17 1894, is a Belgian astronomer who formulated the modern big-bang theory in 1927. He deduced that if the universe was expanding now, then at some point in the distant past all the matter in the universe was in an exceedingly dense state, crushed into a single object.